Booting your OS on real ancient hardware

[rdos]

That's perfectly normal behaviour if you forget to adjust the checksum. Use these steps:
1. save old value to temp
2. write out new value
3. sub temp from checksum
4. add new value to checksum
And you'll be fine. Checksum is stored at CMOS register 2Eh (high byte), 2Fh (low byte).

Yes, except, it was the BIOS itself that updated the values, and then cannot read them correctly after a reboot.

BTW, I also found a site that had some suggestions about how to fix this with a 3v lithium battery, but it seemed pretty complicated, so I think the best is to change to a new chip.

OTOH, I also failed with the old disc. Windows XP could read the partition tables, and copy the files, but RDOS can't. I though there might be some mismatch, but when I try to use Paragon's partition tool, it cannot reformat the disc, and instead encounter disc errors. The other discs I have are newer, and doesn't seem to fit within the sector limits of the old hardware.

So it seems I'm stuck for the moment.

[Owen]

[The thing I love about this Compaq, is that the BIOS setup program comes on a 720kb floppy!

That doesn't sound very good. Chances are that the floppy no longer works. Few of my old floppies work, so that was a real bad choice for backup.

The floppy (miraculously?) works fine. Or, at least, it did last time I dug it out.

If all else fails, HP still (!) have a image of the BIOS setup program on their website. I would just need

• A floppy drive
• A floppy

...These days, I have neither (Well, I have the drive, but I no longer have a port to plug it into)